Spetzler-Martin Grade III Arteriovenous Malformations: A Comparison of Modified and Supplemented Spetzler-Martin Grading Systems

Abstract

BACKGROUND The modified Spetzler-Martin (SM) grading system proposes that grade III arteriovenous malformation (AVM) subtypes are associated with variable microsurgical risks, with small AVMs (III−) having lower risk and medium/eloquent AVMs (III+) having higher risk. Adding patient age and AVM bleeding status and compactness to the SM grade produces a score – the supplemented SM (Supp-SM) grade – to more accurately assess preoperative risk. OBJECTIVE To compare the predictive power of the modified SM and Supp-SM grades for risk assessment in patients with grade III AVMs. METHODS Patients with SM grade III AVMs treated between 2011 and 2018 were retrospectively reviewed. Good outcomes were defined as modified Rankin Scale (mRS) scores ≤ 2 or unchanged/improved mRS scores (pre- vs postsurgery). RESULTS Of 102 patients with SM grade III AVMs, 59% had grade III− and 24% had grade III+ AVMs. Supp SM grade 6 and grade 7 AVMs accounted for 44% and 24%, respectively. Overall, 33% of patients worsened but outcomes did not significantly differ by SM III subtype. Neurological outcomes were associated with Supp-SM grade, with proportions of patients with worsening increasing from 0% with Supp-SM grade 4 AVMs to 54% with Supp-SM grade 7 AVMs. Analyses of factors associated with neurological worsening identified age > 60 yr and Supp-SM grade 7 as significant. CONCLUSION Supp-SM grades were more predictive of microsurgical outcomes than modified SM grades for grade III AVMs, with a hard cutoff for acceptable surgical risk at Supp-SM grade 6. Supp-SM grading is a better decision-making tool than subtyping with the modified SM scale.

Patient frailty association with cerebral arteriovenous malformation microsurgical outcomes and development of custom risk stratification score: an analysis of 16,721 nationwide admissions

“…36,37 Importantly, the AVM-5 is not intended to supplant these existing scores for AVM classification but rather serves as an additional, complementary clinical tool for risk stratification from the alternative perspective of comorbidity burden. While the primary endpoint used to validate the Lawton-Young grade and AVICH was the modified Rankin Scale (mRS) at discharge and followup, [34][35][36][37]42 our AVM-5 score was correlated to several additional outcomes at the inpatient level, including medical complications, LOS, and costs. Each of the AVM-5's variables, excluding hydrocephalus, also has the advantage of being a binary variable easily obtained from chart review and physical examination.…”

Therapeutic Options for Brain Arteriovenous Malformations

“…Classifications have been proposed to estimate risks and benefits. [1,2,4,[8][9][10][11] The most used classification is the Spetzler-Martin classification, which allows the assessment of surgical risk using as criteria the size, location, and presence or absence of deep drainage of the lesion, according to the following punctuation: [1,2,4,[8][9][10][11] • Size: While the classifications above aim to estimate the surgical risk, the Pollock-Flickinger score estimates the likelihood of complete AVM occlusion without neurologic deficit after radiosurgery and is calculated according to the formula: 0.1 x volume in mL + 0.02 x age in years added by 0.5 if the AVM is located in the thalamus, basal ganglia, or brainstem. [1,2]…”

Endovascular treatment in the multimodality management of brain arteriovenous malformations: report of the Society of NeuroInterventional Surgery Standards and Guidelines Committee

“…They suggest that even in lower grade AVMs, adjunctive embolization should be considered to achieve less intraoperative blood loss 33. Spetzler-Martin (SM) grade III AVMs make up a broader group with four subtypes—S1E1V1, S2E0V1, S2E1V0, and S3E0V0—and multiple attempts have been made to delineate the risk of this grade in a nuanced way 34 35. While there is no clear evidence that the risk of hemorrhage meaningfully differs for grade III AVMs from the approximate 2.2% per year baseline natural history risk of rupture for brain AVMs in general,36 the surgical risk increases with the grade.…”